Solid lubricant



Patented Oct. 7, 1941 SOLID LUBRICANT Arnold J. Moi-way, Roselle, andJohn C. Zimmer,

Hillside, N. 1., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application May 6, 1938,

Serial No. 206,412

8Claims.

The present invention relates to improved solid lubricants and morespecifically to greases of the type known as block greases used in thelubrication of heavy journal bearings. and the method of manufacturewill be fully understood from the following description:

' Block greases have been used for many years in the lubrication ofheavy journal bearings such as locomotive journals. These greases areprepared by saponiflcation of fats or fatty acids at high temperaturesin the presence of heavy-mineral oils such as cylinder oils, so as toproduce a fluid mixture which contains from 25 to 50% of soap and thebalance of heavy lubricating oils. The material is held at a hightemperature until it is substantially anhydrous, that. is to saycontaining only very little water, usually less than 1%, and frequentlyabout one-half of 1%. and cools to a greasy solid. The greases are veryhard when cold and have extremely high melting points, in theneighborhood of 300 F. to 400 F. or even 450 F., depending on the amountof soap present and the method by which the melting or softening pointis determined. The major fault with the present block greases is thatthey have The lubricant a rather grainy structure and do not possess asa good lubricating qualities as might be desired, these latter being tosome extent sacrificed in order to gain hardness and the high meltingpoint required for the service.

It has been found that the above difliculties can be overcome by the useof a particular ingredient in the manufacture of the grease. Thismaterial is a byproduct of the low temperature, low pressure airoxidation of paraflln wax with catalysts. It is known that paramn waxmay be oxidized with air in the liquid phase and in the presence of acatalyst such asbarium and manganese soaps at temperatures from 100 to150 C. and at atmospheric or only slightly elevated pressure to yield alarge portion of volatile or distillable fatty acids of the molecularweight range used for soap making. Qther compounds are produced inaddition to the acids, but the material desired for presentmurposes is amaterial of unknown constitutiomprobably polymerized to a considerabledegree so that it is substantially undistillable even under vacuum.

This material may be obtained in various ways from the crudewaxoxidation product, but it is preferred to saponify the fatty materialsunder pressure with aqueous caustic soda,'so as to make a fluidmaterial. Alcohol may be added to prevent emulsiflcation. This productis .then extracted with naphthakerosene or other solvent The averagemolecular weight of this acidic main order to remove most of theunconverted wax. The soap solution is then preferably distilled torecover the alcohol and reacidified so that the acids and other organicmaterial collects in a layer above the aqueous solution and this organiclayer is decanted and distilled under vacuum, so

as to take of! substantially all of the material that can be reasonablydescribed as distillable.

The products obtained as a distillate are largely acids of the soapmaking range, that is containing from 12 to 18 carbon atoms, but it isthe residue which is desired for the present purposes. The chemicalconstitution of this material is not fully understood, but it has beenanalyzed to some extent with the following results:

Per cent Free acids. about--. 30 Esters, lactones, etc Unsaponifiable,about- 5 The total mixture has a neutralization value of about 46 mg.KOH per gram. The saponiflcation value when the mixture is refluxed withKOH is.

Iodine value mg. per gram Neutralization valuemg. KOH per gram 85.5Saponification value (reflux) in KOH mg. per gram 186.9 Saponiflcationvalue (pressure) do 220.5

terial is about 626.5 which is, of course, much higher than most of theknown fatty acids highly unsaturated and free of aldehydes. The materialremaining after removal of free acid has the following characteristics:

Iodine value mg. per gram 82 Saponification value( pressure) per gram115.7 Naphtha soluble per cent. 97.5 Naphtha insoluble do s 2.5Saponifiable do 92.2 Unsaponiflable do 8.6

From the above analyses it would appearthat the vacuum distillationresidue consists of very high molecular weight acids, which are highlyunsaturated, together with unsaturated esters 20% aqueous NaOH, was

and other saponifiable material. The material is polymerized and is ofhigher molecular weight than the wax from which it was obtained.

In making the improved block greases, the above mentioned material whichwill be referred to in this specification and in the claims as anondistillable byproduct of the air oxidation of wax, may be used as thesole soap yielding organic material or it may be admixed with otherfatty materials such as fats and fatty acids. It is preferred to use amajor quantity of this material, however, with only minor amounts offats or fatty acids; for example, while the equal quantities may beused, it is preferredto use 5 to times as much of the wax oxidationproduct as of the low molecular weight fat or fatty'acid. The waxoxidation byproduct or its mixture with fat .or fatty oil is thenadmixed with lubricating oil,

such as a cylinder oil or other viscous lubricating stock. If desired, apart of the cylinder oil may be replaced with petrolatum which alsoimproves the characteristics of the grease. This mixture is meltedtogether by heat to about 160 F., at which temperature aqueous causticsoda is added. The amount of the caustic soda added should be sufiicientto saponify all of the low molecular weight fat which may be present andat least '75 to 85% of the wax oxidation product. If desired the alkaliadded may be sufiicient to neutralize all of the acid groups of the waxoxidation byproduct and free acid may be added such as naphthenic acidor the volatile acids produced by the wax oxidation or other fatty acid.This should be added in proportions from .10 to say 10% of the finalgrease. The mixture is then agitated and the temperature is raised toabout 400 or 450 F., so as to bring about the reaction, and heating iscontinued until a substantially anhydrous material is obtained; that isto say, the water content is reduced below 1%. The material is thenwithdrawn from the kettle and cooled in pans.

As a specific example of the method of manufacturing the grease, thefollowing may be considered:

25 parts of the nondistillable wax oxidation product describedhereinabove were mixed with 2.5 parts of kidney rosin oil and 50 partsof cylinder oil. 20 parts of petrolatum; which had a melting point of150 F., were then added and the mixture was heated to 160 F., at whichtemperature the ingredients melted into a more or less homogeneous fluidmass. Caustic soda solution, then added containing 2.4 parts of dryNaOH, and temperaturewas raised to 420 F. while agitating. The stirringwas continued at this temperaturefor about 1-2 hours, until the productcontained less than 1% water and then was withdrawn and cooled inshallow pans.

The grease was hard but with a smooth and unctuous structure, remarkablyfree from graininess and had the appearance and feel ofa water grease,although it was a dehydrated product and extremely hard. It had amelting point of about 350 F. by the drop method and an A. S. T. M.penetration of 50-100 at 77 F. The present invention is not to belimited by any theory of the use of the various ingredients, nor to anyparticular ingredients or proportions thereof, but only to the followingclaims in which it is desired toclaim all novelty inherent in theinvention.

We claim:

1. An improved block grease comprising mineral oil, a small amount ofkidney-rosin oil and as the main soap ingredient an alkali soap obtainedby saponification of a byproduct of wax oxidation obtained byneutralization of the crude oxidation product removal of unconvertedwax, reaci-clification, and non-destructive distillation of the volatileacids under conditions to leave undisintegrated said non-distillableacidic residue byproduct free from acid having not more than 18 carbonatoms and the acids present having an average molecular weight of atleast about 600.

2. An improved block grease comprising a heavy mineral oil, a smallamount of kidney rosin oil and at least 25% of an alkali soap of anonvolatile acidic material obtained by saponifying a crude oxidationproduct, removing unconverted wax reacidifying with mineral acid anddistilling. oif the volatile organic acids under high vacuum so as torecover a non-distillable acidic residue the acids present in which havean average molecular weight of at least about 600 and are free fromacids having not more than 18 carbon atoms which is used in thepreparation of the soap.

3. Product according to claim 2 in which the grease contains a smallamount of a soap of a fatty acid.

4. Product according to claim 2 in which the grease comprises about 25parts of the non-volatile oxidation product, 2% parts of kidney rosinoil, about '70 parts of heavy hydrocarbons, and caustic soda suflicientto saponify the kidney rosin oil and at least 75% of the oxidationproduct.

5. Product according to claim 2 in which the oil is a cylinder oil andpetrolatum is added thereto.

6. A block grease comprising mineral oil, a small amount of kidney rosinoil and, as the main soap ingredient, an alkali soap of a high molecularweight non-distillable unsaturated polymerized acidic residue obtainedas a by-product of wax oxidation, which is free from acids having 18 orless carbon atoms and which is substantially free from unconverted wax,arid the acid content of said acidic residue having an average molecularweight of at least about 600.

7. A solid lubricating grease having a hard, smooth, unctuous structuresubstantially free from graininess, having a melting point of about 350R, an A. S. T. M. penetration of about 50-100 at 77 F., and containingless than about 1% of water, said grease being made from the followingmaterials using approximately the proportions indicated:

High molecular weight non-distillable polymerized wax-oxidation acidicby-product having a saponification value of about 175 mg. KOH per gramand consisting essentially of about 30% of unsaturated free acids havingan average molecular weight of about 626.5 and free from acids having 18or less carbon atoms, the balance of said acidic by-product being analdehyde-free mixture of about 65% of esters, lactones; etc. and about5% of unsaponifiable material parts 25 Kidney rosin oil do 2.5 Cylinderoil do 50 Petrolatum (melting point about v F.)

parts 20 Caustic soda solution (20% concentration) containing parts ofdry NaOH 2.4

Total parts 99.9

8, The process of preparing a dehydrated block grease which comprisesmelting and heating to about 160 F. a mixture of a mineral oil, a smallamount of kidney rosin oil and a high molecular weight non-distillableacidic residue obtained as a by-product from the oxidation of paraflinwax, said residue being free from acids having 18 or less carbon atomsbut said residue having a free- I acid content having an averagemolecular weight A of at least about 600 and said residue having avneutralization value of about 46 mg. KOH per gram, 2. saponificationvalue, refluxed, of about 175 mg. KOH per gram and a, pressuresaponification value of about 230 mg. KOH per gram,

adding to the above-formed mixture 2. suflicient amount of aqueouscaustic soda solution to sapom'fy at least 75% of the free acid contentof the wax oxidation product, agitating, and heating the mixture toabout 400 F. to complete the re-

